Conventionally, various wires are used for establish electrical connection between components provided in industrial apparatuses, robots, game machines, and the like as well as various electronic apparatuses such as communication and video apparatuses. Particularly, a cable bear (registered trademark), for example, is used in portions where smooth movement of components in apparatuses is required (see PTL I). However, according to this technique, since members for supporting cables and the like are required, the cable bears require relatively large space for arrangement. In contrast, the use of a flexible printed wiring board enables the arrangement space to be narrowed. However, when an ordinary flexible printed wiring board is used as it is, the flexible printed wiring board sags. Therefore, it is impossible to employ an ordinary flexible printed wiring board without modification, depending on the position where the board is used. In contrast, a technique in which a flexible printed wiring board is molded in a state of being curved in a lateral direction so that the board does not sag is known (see PTL 2 and 3). This technique will be described with reference to FIGS. 22 and 23. FIG. 22 is a perspective view of an ordinary flexible printed wiring board. FIG. 23 is a perspective view of a flexible printed wiring board according to a related art.
In an ordinary flexible printed wiring board 500, when one and another ends in a longitudinal direction of the board are fixed respectively to one and another members (not illustrated) that move in relation to each other, the flexible printed wiring board 500 sags (see FIG. 22). Due to this, when the sagging flexible printed wiring board 500 makes contact with various components and inconvenience occurs, it is impossible to use the board. In contrast, in a flexible printed wiring board 600 molded in a state of being curved in a lateral direction, even when one and another ends in a longitudinal direction are fixed respectively to one and anther members that move in relation to each other, the board is self-supported and does not sag (see FIG. 23). In FIG. 23, R1 indicates the radius of curvature of a curved portion that is bent to be curved in the longitudinal direction in order to fix one and the other ends in the longitudinal direction of the flexible printed wiring board 600 to respectively to the one and the other members that move in relation to each other. R2 indicates the radius of curvature of a curved portion that is curved in the lateral direction of the flexible printed wiring board 600.
Here, it is experimentally proven that the radii of curvature R1 and R2 are correlated and these values are approximately equal to each other. Therefore, when the number of wires in the flexible printed wiring board 600 is increased, since the width (the width in the lateral direction) increases, the radius of curvature R2 increases and the radius of curvature R1 also increases. As a result, the distance in the height direction (up-down direction) in FIG. 23 also increases.
Due to this, depending on the space in which the flexible printed wiring board 600 is disposed, since the width of the flexible printed wiring board 600 is limited and the number of wires is also limited, the degree of freedom for design decreases.